Enhanced performance in bulk heterojunction solar cells by introducing naphthalene derivatives as processing additives

Naphthalene derivatives such as 1-fluoronaohthalene, 1-chloronaohthalene, 1-bromonaohthalene, and 1-iodonaohthalene were introduced to poly (3-hexylthiophene) (P3HT): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)-based bulk heterojunction (BHJ) polymer solar cells (PSCs) as processing additives. To investigate why the addition of naphthalene derivatives improved the efficiency of PSCs, the photon absorbance properties were observed using UV–vis spectroscopy and photoluminescence (PL). Then, the degree of crystallinity of P3HT was examined through X-ray diffraction (XRD) analysis. In addition, changes in the nanostructure and surface morphology of the P3HT:PC61BM blend film were observed through atomic force microscopy (AFM) and transmission electron microscopy (TEM). The series resistance (RS) and shunt resistance (RSH) of the fabricated PSCs were 8.77 Ω cm2 and 2337 Ω cm2, respectively. The short circuit current density (JSC), open circuit voltage (VOC), and fill factor (FF) were 9.7 mA/cm2, 0.636 V, and 63.6%, respectively. As a result, the power conversion efficiency (PCE) was 3.9%.