It is widely known that solvent engineering has a significant effect on the growth of high quality perovskite film. However, the crystal evolution process and crystal compositions of perovskite film when applying the two-step method are multifaceted, and the effects on the photoelectrical properties for the perovskite layer still require further study. In this study, the above two issues are systematically studied. Combining the XRD and photoluminescence spectra results, it was observed that the residual PbI2 decreased with the increase of DMSO in DMSO/DMF solvents and that there were two types of local phase crystallites (disordered and ordered) in the perovskite films. The phase transitions of the crystals were investigated with the ratio of DMSO increasing in the mixed solvents. In addition, the interfacial defect states in the PbI2/perovskite interface which can act as charge carrier trapping centers were significantly affected by the photo(dark) conductivity of the perovskite film. It was also observed that the photoconductivity of the perovskite film with the DMSO 30%, which contains mixed-phase (ordered/disordered) crystals and trace amounts of PbI2, was higher than the film with DMSO 60%. Finally, a high power conversion efficiency of 16.5% with trace amounts of PbI2 was achieved when the volume ratio of the DMSO was 30%.

It is widely known that solvent engineering has a significant effect on the growth of high quality perovskite film. However, the crystal evolution process and crystal compositions of perovskite film when applying the two-step method are multifaceted, and the effects on the photoelectrical properties for the perovskite layer still require further study. In this study, the above two issues are systematically studied. Combining the XRD and photoluminescence spectra results, it was observed that the residual PbI2 decreased with the increase of DMSO in DMSO/DMF solvents and that there were two types of local phase crystallites (disordered and ordered) in the perovskite films. The phase transitions of the crystals were investigated with the ratio of DMSO increasing in the mixed solvents. In addition, the interfacial defect states in the PbI2/perovskite interface which can act as charge carrier trapping centers were significantly affected by the photo(dark) conductivity of the perovskite film. It was also observed that the photoconductivity of the perovskite film with the DMSO 30%, which contains mixed-phase (ordered/disordered) crystals and trace amounts of PbI2, was higher than the film with DMSO 60%. Finally, a high power conversion efficiency of 16.5% with trace amounts of PbI2 was achieved when the volume ratio of the DMSO was 30%.

Molybdenum disulfide (MoS2), as a typical two-dimensional (2D) material, has attracted extensive attention in recent years because of its fascinating optical and electric properties. However, the applications of MoS2 have been mainly in photovoltaic devices, field-effect transistors, photodetectors, and gas sensors. Here, it is demonstrated that MoS2 can be found another important application in position sensitive detector (PSD) based on lateral photovoltaic effect (LPE) in it. The ITO/MoS2(3, 5, 7, 9, 10, 20, 50, 100 nm)/p-Si heterojunctions were successfully prepared with vertically standing nanosheet structure of MoS2. Because of the special structure and the strong light absorption of the relatively thick MoS2 film, the ITO/MoS2/p-Si heterojunction exhibits an abnormal thickness-dependent LPE, which can be ascribed to the n- to p-type transformation of MoS2. Moreover, the LPE of ITO/MoS2/p-Si structure improves greatly because of forward enhanced built-in field by type transformation in a wide spectrum response ranging from visible to near-infrared, especially the noticeable improvement in infrared region, indicating its great potential application in infrared PSDs. This work not only suggest that the ITO/MoS2/p-Si heterojunction shows great potential in LPE-based sensors, but also unveils the importance of type transformation of MoS2 in MoS2-based photoelectric devices besides strong light absorption and suitable bandgap.Keywords: broadband; ITO/MoS2/p-Si heterojunction; position sensitive detector; Schottky barrier; type transformation;

•The a-SiOx:H microstructure has a great impact on silicon surface passivation.•How and why the microstructure influences the passivation quality is illustrated.•With a compact a-SiOx:H, the superior c-Si surface passivation is obtained.•The HIT solar cells with Voc of 0.702 V and efficiency of 20.4% are achieved.•The photoresponse of HIT solar cells is significantly improved.The microstructure of the intrinsic amorphous silicon oxide (i-a-SiOx:H) thin films is the key for crystalline silicon surface passivation in high-performance HIT solar cells. Understanding and subsequently optimizing the i-a-SiOx:H microstructure is essential in improving defect passivation and carrier transportation in a-SiOx:H films. In this work, we investigate the relationship between the bulk microstructure of i-a-SiOx:H thin films at different oxygen content and the passivation quality of the silicon surface. The results revealed that, as the oxygen content increases, the dominating growth mechanism of i-a-SiOx:H films changes. Consequently, the component contents of i-a-SiOx:H thin films were varied and the microstructure showed a first improved and then deteriorated trend with increasing oxygen content. A compact, less-defective and ordered microstructure of the a-SiOx:H film can only be obtained when there comes a tradeoff between SiO and SiH(Si3) bonding formation. Correspondingly, the improved defect passivation and the enhanced carrier transportation in a-SiOx:H films lead to the increase of Voc, FF and QE of HIT solar cells, all of which are key solar cell performance parameters.

In this paper, we prepared silicon heterojunction (SHJ) solar cells with the structure of p-c-Si/i-a-SiOx:H/n-μc-SiOx:H (a-SiOx:H, oxygen rich amorphous silicon oxide; μc-SiOx:H, microcrystalline silicon oxide) by plasma-enhanced chemical vapor deposition method. The influence of the n-μc-SiOx:H emitter thickness on the heterointerface passivation in SHJ solar cells was investigated. With increasing thickness, the crystallinity of the emitter as well as its dark conductivity increases. Meanwhile, the effective minority carrier lifetime (τeff) of the SHJ solar cell precursors at low injection level shows a pronounced increase trend, implying that an improved field effect passivation is introduced as the emitter is deposited. And, an increased τeff is also observed at entire injection level due to the interfacial chemical passivation improved by the hydrogen diffusion along with the emitter deposition. Based on the analysis on the external quantum efficiency of the SHJ solar cells, it can be expected that the high efficient SHJ solar cells could be obtained by improving the heterointerface passivation and optimizing the emitter deposition process.

•Phosphorus doped Si-quantum-dots/SiO2 films have been prepared.•Carrier capture centers at the interface were filled by phosphorus doping.•The optoelectronic properties of films were enhanced by proper doping.Phosphorus (P) doped Si-quantum-dots/SiO2 multilayer films have been deposited by plasma enhanced chemical vapor deposition (PECVD) technique, and Si quantum dots (Si-QDs) are obtained by the following annealing treatment. Raman and transmission electron microscopy (TEM) results show that P doping prevents the growth of Si-QDs. The photoluminescence (PL) intensity can be enhanced by proper P doping, and a maximal PL intensity is obtained when the doping flow ratio of phosphine and silicane is 0.75%. The resistivity of the films is reduced by P doping, and proper doping leads two orders of magnitude lower than that of the intrinsic films. Analysis shows that proper P doping in the multilayer films could fill the carrier capture center in interface and suppress the non-radiative recombination of carriers.

Alternating multilayer films of hydrogen diluted hydrogenated protocrystalline silicon (pc-Si:H) were prepared using a plasma- enhanced chemical vapor deposition technique. The microstructure of the deposited films and photoresponse characteristics of their Schottky diode structures were investigated by Raman scattering spectroscopy, Fourier transform infrared spectroscopy and photocurrent spectra. Microstructure and optical absorption analyses suggest that the prepared films were pc-Si:H multilayer films with a two-phase structure of silicon nanocrystals (NCs) and its amorphous counterpart and the band gap of the films showed a decreasing trend with increasing crystalline fraction. Photocurrent measurement revealed that silicon NCs facilitate the spatial separation of photo-generated carriers, effectively reduce the non-radiative recombination rate, and induce a photoresponse peak value shift towards the short-wavelength side with increasing crystallinity. However, the carrier traps near the surface defects of silicon NCs and their spatial carrier confinement result in a significant reduction of the diode photoresponse in the long-wavelength region. An enhancement of the photoresponse from 350 to 1000 nm was observed when applying an increased bias voltage in the diode, showing a favorable carrier transport and an effective collection of photo-generated carriers was achieved. Both the spatial separation of the restricted electron-hole pairs in silicon NCs and the de-trapping of the carriers at their interface defects are responsible for the red-shift in photoresponse spectra and enhancement of external quantum efficiency. The results provide fundamental data for the carrier transport control of high-efficiency pc-Si:H solar cells.

We report on the synthesis of Si nanocrystallites by pulsed laser ablation in toluene followed by the preparation of composite films with PMMA and their luminescence studies. Transmission electron microscopy images show that the sizes of silicon nanocrystallites vary from about 4 nm down to below 1 nm. The composite films exhibit strong emissions with their spectral peaks continuously moving from 387 to 506 nm when the excitation wavelength varies from 300 to 440 nm, in accordance with the quantum confinement effect. Their time-resolved photoluminescence spectra reveal a multi-exponential decay, implying that the light emission may be also related to some surface states.

In this paper, we prepared silicon heterojunction (SHJ) solar cells with the structure of p-c-Si/i-a-SiOx:H/n-μc-SiOx:H (a-SiOx:H, oxygen rich amorphous silicon oxide; μc-SiOx:H, microcrystalline silicon oxide) by plasma-enhanced chemical vapor deposition method. The influence of the n-μc-SiOx:H emitter thickness on the heterointerface passivation in SHJ solar cells was investigated. With increasing thickness, the crystallinity of the emitter as well as its dark conductivity increases. Meanwhile, the effective minority carrier lifetime (τeff) of the SHJ solar cell precursors at low injection level shows a pronounced increase trend, implying that an improved field effect passivation is introduced as the emitter is deposited. And, an increased τeff is also observed at entire injection level due to the interfacial chemical passivation improved by the hydrogen diffusion along with the emitter deposition. Based on the analysis on the external quantum efficiency of the SHJ solar cells, it can be expected that the high efficient SHJ solar cells could be obtained by improving the heterointerface passivation and optimizing the emitter deposition process.

•A novel selenization process is used to prepare Cu2Zn(Sn,Ge)(S,Se)4 (CZTGSSe) thin films.•Ge element is incorporated successfully into the material and large crystal grains are observed in the CZTGSSe layers.•Based on the CZTGSSe absorber, solar cells with efficiencies up to 9.1% could be fabricated.A novel selenization process is used to prepare Cu2Zn(Sn,Ge)(S,Se)4 (CZTGSSe) thin films. During this selenization process, Ge is introduced into the solution deposited precursors from a GeSe2 source and assists the formation and crystallization of CZTGSSe. The composition, morphology and phases for the selenized films are investigated and solar cells are prepared. The results suggest Ge is incorporated into the material and no obvious secondary phases except ZnSe are detected in CZTGSSe. The obtained CZTGSSe layers are constituted of large crystal grains and show uniform morphology. Based on the CZTGSSe absorber, solar cells with efficiencies up to 9.1% can be fabricated.