Influence of Poly(Vinylidene fluoride) on photovoltaic performance of interfacially engineered band gap modulated P3TAA-co-P3HT perovskite solar cell at ambient condition

Recently, mixing of foreign polymers with perovskite increases light absorption yielding a large increase of power conversion efficiency (PCE) and also increasing longevity of perovskite solar cells (PSCs). The previous studies are limited at dry or at very low humid conditions. Here, for practical use, we report a new series of poly(vinylidene fluoride) (PVDF)-perovskite (MAPbI3) hybrid solar cells made from different PVDF concentrations e.g. 0.0, 0.25, 0.5, 1.0, 2.5, 5.0 mg/ml, and are designated as H1, H2, H3, H4, H5, and H6, respectively. The average grain size, measured from SEM images of MAPbI3 (312 ± 91 nm) has decreased with increasing PVDF concentration showing a minimum (215 ± 43 nm) for H5 sample. UV–Vis absorption spectra show the highest absorption for H5 sample for all the wavelengths. The intensities and width of X-ray diffraction peaks increase in the hybrids (H3 and H5) from pristine perovskite indicating increase of crystallinity and crystalline size. We have used an interfacially engineered, band gap modulated poly(3-thiophene acetic acid)–co-poly(3-hexyl thiohene) P3TTA - co - P3HT, with 43 mol% P3TAA content as hole transporting material (HTM) and TiO2 as electron transporting material (ETM) to fabricate the cell. The PCE, measured on illumination with a light of one sun at ambient condition (humidity 75–85%, temperature 30 °C), is 12% for H5 PSC, highest reported so far, and it is 20% higher from pristine PSC. The incident photon to current conversion efficiency (IPCE) data exhibit strong absorption in the broad range 300–800 nm showing a maximum IPCE value of 84%. Impedance spectral data indicate that lifetime of photo-generated charges are highest (48.4 m s) explaining the highest PCE value for H5-PSC compared to other hybrids. The longevity of the H5-PSC is significantly (54%) higher than PSC made with pristine perovskite measured and stored under identical ambient condition.