Engineering of extended peripheral acceptor moieties into imide pyrrole based materials for promising photovoltaic properties: A quantum chemical approach

Abstract

Herein, a series of NFA-based (DPP1-DPP6) chromophores were designed rationally by altering the terminal acceptors of (DPPR) reference chromophore, while retaining the selenophene π-spacer and central acceptor unit (A2) same. DFT and TD-DFT calculations were performed by using the M06/6-311G(d,p) functional to explore their photovoltaic properties. FMOs analysis unveiled that DPP1-DPP6 molecules showed narrow band gaps and broader absorption spectra in the visible range as compared to DPPR. The increasing order of λ_max of aforementioned chromophores is found as DPPR < DPP1 <DPP2 <DPP6 <DPP3 <DPP4 <DPP5 in chloroform solvent. Particularly, DPP5 exhibited the maximum absorption peak at 636.105 nm and the lowest transition energy of 1.949 eV, mainly because of terminal electron-withdrawing acceptor groups. Interestingly, all derivatives exhibited lower E_b values (0.597–0.630 eV) compared to the reference (0.636 eV) which implied a faster rate of exciton dissociation and enhanced charge transfer compared to DPPR, and further supported by DOS and TDM analyses. Moreover, a notable photovoltaic response in terms of V_oc was observed for all examined compounds, suggesting their potential suitability for future use. Thus, our study urges experimentalists to synthesize these organic systems to achieve high efficiency photovoltaic devices. This work uncovers that introducing groups into NFAs is a fruitful approach for advancing OSCs, and the findings disclosed herein are supportive to designing new NFAs.