Liquid-phase crystallized silicon absorber layers have been applied in heterojunction solar cells on glass substrates with 10.8% conversion efficiency and an open-circuit voltage of 600 mV. Intermediate layers of SiO x , SiN x , and SiO x N y , as well as the a-Si:H precursor layer, were deposited on 30 cm × 30 cm glass substrates using industrial-type plasma-enhanced chemical vapor deposition equipment. After crystallization on 3 cm × 5 cm area using a continuous-wave infrared laser line, the resulting polysilicon material showed high material quality with large grain sizes. Index Terms-Heterojunction, liquid-phase crystallization, plasma-enhanced chemical vapor deposition (PECVD), thin-film silicon.

Thin crystalline silicon solar cells prepared directly on glass substrates by means of liquid-phase crystallization of the absorber utilize only a small fraction of the silicon material used by standard wafer-based silicon solar cells. The material consists of large crystal grains of up to square centimeter area and results in solar cells with open-circuit voltages of 650 mV, which is comparable with results achieved with multi-crystalline silicon wafers. We give a brief status update and present new results on the electronic interface and bulk properties. The interrelation between surface passivation and additional hydrogen plasma passivation is investigated for p-type and n-type absorbers with different doping concentrations. Internal quantum efficiency measurements from both sides on bifacial solar cells are used to extract the bulk-diffusion length and surface-recombination velocity. Finally, we compare various types of solar cell devices based on 10 μm thin crystalline silicon, where conversion efficiencies of 11-12% were achieved with p-type and n-type liquid-phase crystallized absorbers on glass.

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We present an interdigitated back-contact silicon heterojunction system designed for liquid-phase crystallized thin-film (~10 μm) silicon on glass. The preparation of the interdigitated emitter (a-Si:H(p)) and absorber (a-Si:H(n)) contact layers relies on the etch selectivity of doped amorphous silicon layers in alkaline solutions. The etch rates of a-Si:H(n) and a-Si:H(p) in 0.6% NaOH were determined and interdigitated back-contact silicon heterojunction solar cells with two different metallizations, namely Al and ITO/Ag electrodes, were evaluated regarding electrical and optical properties. An additional random pyramid texture on the back side provides short-circuit current density (j SC ) of up to 30.3 mA/cm 2 using the ITO/Ag metallization. The maximum efficiency of 10.5% is mainly limited by a low of fill factor of 57%. However, the high j SC , as well as V OC values of 633 mV and pseudo-fill factors of 77%, underline the high potential of this approach.

The influence of the transparent conducting oxide (TCO) topography was studied on the performance of a silicon oxide intermediate reflector layer (IRL) in a-Si/μc-Si tandem cells, both experimentally and by 3-D optical simulations. Therefore, cells with varying IRL thickness were deposited on three different types of TCOs. Clear differences were observed regarding the performance of the IRL as well as its ideal thickness, both experimentally and in the simulations. Optical modeling suggests that a small autocorrelation length is essential for a good performance. Design rules for both the TCO topography and the IRL thickness can be derived from this interplay. Index Terms-3-D rigorous optical modeling, a-Si/μc-Si, intermediate reflector, micromorph, solar cells, transparent conducting oxide (TCO). I. INTRODUCTION AND BACKGROUND A S THE demand for affordable clean energy grows, amorphous silicon (a-Si) / microcrystalline silicon (μc-Si) tandem solar cells are an interesting technology, as it combines nontoxic and abundant materials with a low temperature/low cost process. However, the conversion efficiency of these de-Manuscript