Thin‐film (25.5 μm) solar cells from layer transfer using porous silicon with 32.7 mA/cm² short‐circuit current density

Abstract

We fabricate a 25.5‐μm‐thick monocrystalline Si solar cell with a confirmed power conversion efficiency of 15.4% and an area of 3.88 cm2 using a layer transfer process with porous Si. The process is free of photolithography and contains no high‐temperature oxidation steps. We investigate three design features that improve the short‐circuit current density to a value of 32.7 mA/cm2 under AM1.5 illumination. The detached back reflector contributes 2 mA/cm2, a reduced front‐surface reflectance accounts for an additional 2 mA/cm2 and a reduced base doping increases the current density by 1 mA/cm2. Copyright © 2002 John Wiley & Sons, Ltd.

Comparison of periodic light-trapping structures in thin crystalline silicon solar cells

“…Fabrication of significantly thinner sheets of high quality Si with a thickness below 20 lm has been demonstrated by various techniques. [1][2][3] Throughout this work, we use a Si thickness of 20 lm as a case of study when exploring the light-trapping ability of the various structures. This is thinner than today's wafer-based solar cells by a factor of 10 and at the same time thicker than ordinary thinfilm solar cells by a factor of 10.…”

Very Thin (56 μm) Silicon Heterojunction Solar Cells with an Efficiency of 23.3% and an Open‐Circuit Voltage of 754 mV

“…PV properties of various c‐Si solar cells as a function of c‐Si wafer/absorber thickness, w : a) V OC , b) J SC , c) FF, and d) efficiency. The difference in symbol types indicates the different approaches for preparing the thin c‐Si absorber and the cell architectures: standard slicing or thinning (SHJ cells [ 9,20,31,34,36–40,55–57 ] including heteroback contacts [ 30,32,33,55 ] and other types [ 6,8,9,11,18,58–62 ] ), epitaxially grown c‐Si films, [ 12–20,27 ] SOI, [ 24 ] exfoliated Si films, [ 19 ] and polycrystalline Si films. [ 25,26 ] The filled symbols represent data for cells which have been independently confirmed.…”

“…Experimentally, thin ( w < 100 μm) and very thin ( w < 70 μm) c‐Si cells have been investigated based on various technologies such as sliced/thinned free‐standing wafers, [ 6–11 ] epitaxially grown Si thin layers, [ 12–20 ] exfoliated Si films, [ 19,21 ] Si on insulator (SOI) wafers, [ 22–24 ] and polycrystalline Si thin films. [ 25,26 ] The first very thin c‐Si cell having η > 20% was demonstrated by Wang et al in 1996, [ 6 ] whereby a 21.5% efficient passivated emitter rear locally diffused (PERL) cell was fabricated using float‐zone (FZ) Si wafers ( w = 47 μm) and thinned by chemical etching.…”

“…It is worth noting that the efficiency limit is dependent on light trapping scheme and numerical simulation has predicted that η > 30% is possible for very thin c-Si cells (15 μm) by applying advanced light trapping using photonic crystals. [4,5] Experimentally, thin (w < 100 μm) and very thin (w < 70 μm) c-Si cells have been investigated based on various technologies such as sliced/thinned free-standing wafers, [6][7][8][9][10][11] epitaxially grown Si thin layers, [12][13][14][15][16][17][18][19][20] exfoliated Si films, [19,21] Si on insulator (SOI) wafers, [22][23][24] and polycrystalline Si thin films. [25,26] The first very thin c-Si cell having η > 20% was demonstrated by Wang et al in 1996, [6] whereby a 21.5% efficient passivated emitter rear locally diffused (PERL) cell was fabricated using float-zone (FZ) Si wafers (w ¼ 47 μm) and thinned by chemical etching.…”

Silicon-Based Technologies for Flexible Photovoltaic (PV) Devices: From Basic Mechanism to Manufacturing Technologies

“…In the bending experiments, an efficiency of 14.6% was independently confirmed after the film was transferred to a flexible plastic foil [64]. Solar cells prepared by transfer technology have achieved conversion efficiencies of up to 16% [63,65].…”