Flexible crystalline silicon radial junction photovoltaics with vertically aligned tapered microwires†
Much attention has been paid to thin crystalline silicon (c-Si) photovoltaic devices due to their excellent flexibility characteristics, stable efficiency, and possibility of use as highly efficient next-generation flexible photovoltaic devices (FPVs). To fabricate thin c-Si FPVs, it is important to improve their light-absorption properties while maintaining the flexible characteristics. In this study, vertically aligned microwires (MWs) on a 50 μm-thick thin c-Si substrate are designed for novel FPVs. Increasing the length of the MWs enhances the optical properties of the thin c-Si without affecting its flexibility. To maximize the efficiency of the thin c-Si FPVs with MWs, tapered MWs and a localized back-contact structure are devised. This device shows a maximum efficiency of 18.9%. In addition, the proposed thin c-Si FPV with MWs shows high stability without any change in efficiency, even with 1000 bending cycles with a bending radius of 12 mm. Thus, we successfully demonstrate battery-free flexible electronic devices integrated with our thin c-Si FPVs with MWs.