Self-Assembled, Highly Crystalline Porous Ferroelectric Poly (Vinylidene Fluoride-co-Trifluoroethylene) interlayer for Si/Organic Hybrid Solar Cells
Sung Bum Kang (Advisor: Kyoung Jin Choi)
Nano energy 2017, 41, 243-250

Ferroelectric polymers can effectively improve the photovoltaic performance of solar cells, inducing an electric field to promote the dissociation of electron-hole pairs, with the thus generated charges collected from open pores. Since such performance enhancement requires materials with a unique porous crystalline structure, we herein present a novel route to highly crystalline and porous poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) thin films utilizing a modified breath figure method based on spin coating. The key feature of the above method is the addition of small amounts of water to the acetone/P(VDF-TrFE) solution to produce porous ferroelectric thin films which have significantly higher crystallinity values than nanostructures or films prepared by other methods. Furthermore, n-Si / poly(3,4-ethylene dioxy thiophene):poly(styrene sulfonate) hybrid solar cells with porous P(VDF-TrFE) interlayers are demonstrated to exhibit spontaneous polarization sufficient for increasing their open circuit voltages and fill factors. Finite-difference time-domain simulation reveals that the electric field due to the above spontaneous polarization increases the built-in electric field of the Schottky junction between n-Si and poly(3,4-ethylene dioxy thiophene):poly(styrenesulfonate) and reduces the reverse leakage current of the Schottky diode. Thus, the organic ferroelectric thin films with controlled porosity proposed in this study are well suited for a broad range of optoelectronic applications.