Solution processing of inorganic thin fi lms has become an important thrust in material research community because it offers low-cost and high-throughput deposition of various functional coatings and devices. Especially inorganic thin fi lm solar cells -macroelectronic devices that rely on consecutive deposition of layers on large-area rigid and fl exible substrates -could benefi t from solution approaches in order to realize their low-cost nature. This article critically reviews existing deposition approaches of functional layers for chalcogenide solar cells with an extension to other thin fi lm technologies. Only true solutions of readily available metal salts in appropriate solvents are considered without the need of pre-fabricated nanoparticles. By combining three promising approaches, an air-stable Cu(In,Ga)Se 2 thin fi lm solar cell with effi ciency of 13.8% is demonstrated where all constituent layers (except the metal back contact) are processed from solutions. Notably, water is employed as the solvent in all steps, highlighting the potential for safe manufacturing with high utilization rates. remarkable improvements in conversion effi ciency. [ 1 ] The highest effi ciency of 21.0% has been achieved for two thin fi lm technologies so far: Cu(In,Ga)Se 2 (CIGS) [ 2 ] and CdTe. [ 3 ] Remarkably, both CIGS and CdTe records are exceeding the highest value of 20.4% for the market leading polycrystalline silicon wafer technology. Kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells are often considered as low-cost alternatives to CIGS and CdTe because they consist of only earth-abundant and nontoxic elements although the effi ciency is currently limited to 12.6% (12.7% not certifi ed). [ 4 ] Well-established dye-sensitized solar cell (DSSC) and amorphous silicon (a-Si) technology peak at 12.3% and 13.4%, respectively. [ 1 ] The most recent boom in TFPV -organometallic halide perovskite cells -has shown an incredible spurt by advancing effi ciency from below 5% to 17.9%(!) within just 3 years. [ 5 ] On the border to classical TFSC is the thin crystalline silicon technology that employs liftoff of 50-micrometer-thick Si wafers to yield up to 21.2%-efficient solar cells. [ 6 ] These massive research and development efforts in the fi eld of TFSC clearly refl ect their commercial value for manufacturing inexpensive effi cient solar modules -rigid or fl exible. Functional layers for the high effi ciency devices are deposited mostly in a batch-to-batch manner using vacuum-based methods such as evaporation, sputtering, or chemical vapor deposition. For example, Figure 1 exhibits a cross-section of a >20% effi cient CIGS solar cell in the so-called substrate confi guration, where 5 out of 6 functional layers are deposited by evaporation or sputtering. In this respect, non-vacuum deposition methods are often promoted as alternative approaches to reduce capital investment costs, offer fast roll-to-roll (R2R) processing and eventually reduce the PV module prices. Particularly desirable among non-vacuum approaches are solutionb...

This work reports the detailed Raman scattering analysis of Cu-poor Cu(In,Ga)Se2 (CIGS) electrodeposited solar cells using different excitation wavelengths. The systematic assessment of cells fabricated with Cu-poor absorbers that were synthesized with different Cu contents has allowed identifying the existence of a quasi-resonant excitation of a Raman peak characteristic of an Ordered Vacancy Compound (OVC) secondary phase when using a 785 nm excitation wavelength. The enhanced sensitivity of the spectra measured with these conditions to the presence of the OVC phase provides with a suitable tool for the non destructive assessment on the occurrence of this Cu-poor secondary phase in the surface region of the CIGS absorbers from measurements performed on finished cells. The correlation between the Raman scattering data and the optoelectronic parameters of the devices shows the existence of an optimum OVC content range leading to devices with highest open circuit voltage and efficiency. These data provide with a clear experimental evidence on the impact of the OVC phases on the device efficiency.

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This paper presents the low cost electrodeposition of a transparent and conductive chlorine doped ZnO layer with performances comparable to that produced by standard vacuum processes. First, an in-depth study of the defect physics by ab-initio calculation shows that chlorine is one of the best candidates to dope the ZnO. This result is experimentally confirmed by a complete optical analysis of the ZnO layer deposited in a chloride rich solution. We demonstrate that high doping levels (>1020 cm−3) and mobilities (up to 20 cm2 V−1 s−1) can be reached by insertion of chlorine in the lattice. The process developed in this study has been applied on a CdS/Cu(In,Ga)(Se,S)2 p-n junction produced in a pilot line by a non vacuum process, to be tested as solar cell front contact deposition method. As a result efficiency of 14.3% has been reached opening the way of atmospheric production of Cu(In,Ga)(Se,S)2 solar cell.

In this work, the fabrication of MoOx-free semitransparent perovskite solar cells (PSC) with Power Conversion Efficiencies (PCE) up to 15.7% is reported. Firstly, opaque PSCs up to 19.7% were fabricated. Then, the rear metal contact was replaced by a highly transparent and conductive indium tin oxide (ITO) film, directly sputtered onto the hole selective layer, without any protective layer between Spiro-OMeTAD and rear ITO. To the best of our knowledge, this corresponds to the most efficient buffer layer-free semitransparent PSC ever reported. Using time-resolved photoluminescence (TRPL) technique on both sides of the semitransparent PSC, Spiro-OMeTAD/perovskite and perovskite/TiO2 interfaces were compared, confirming the great quality of Spiro-OMeTAD/perovskite interface, even after damage-less ITO sputtering, where degradation phenomena result less important than for perovskite/TiO2 one. Finally, a 4-terminal tandem was built combining semitransparent PSC with a commercially-available Aluminium Back Surface Field (Al-BSF) silicon wafer. That silicon wafer presents PCE = 19.52% (18.53% after being reduced to cell size), and 5.75% once filtered, to generate an overall 4 T tandem efficiency of 21.18% in combination with our champion large semitransparent PSC of 15.43%. It means an absolute increase of 1.66% over the original silicon wafer efficiency and a 2.65% over the cut Si cell.