Molecular engineering of several butterfly-shaped hole transport materials containing dibenzo[b,d]thiophene core for perovskite photovoltaics

Abstract

Several butterfly-shaped materials composed of dibenzo[b,d]thiophene (DBT) and dibenzo-dithiophene (DBT5) cores were designed as hole transporting materials (HTMs) and their properties were studied by density functional theory (DFT) computations for usage in mesoscopic n-i-p perovskite solar cells (PSCs). To choose suitable HTMs, it was displayed that both of lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energies of molecules were located higher than those of CH3NH3PbI3 (MAPbI3) perovskite as they were able to transfer holes from the MAPbI3 toward Ag cathode. Negative solvation energy (ΔEsolvation) values for all HTMs (within the range of − 5.185 to − 18.140 kcal/mol) revealed their high solubility and stability within CH2Cl2 solvent. The DBT5-COMe demonstrated the lowest values of band gap (Eg = 3.544) and hardness (η = 1.772 eV) (the greatest chemical activity) and DBT5-CF3 displayed the biggest η = 1.953 eV (maximum stability) that were predominantly valuable for effective HTMs. All HTMs presented appropriately high LHEs from 0.8793 to 0.9406. In addition, the DBT5 and DBT5-SH depicted the lowest exciton binding energy (Eb) values of 0.881 and 0.880 eV which confirmed they could produce satisfactory results for the PSCs assembled using these materials. The DBT5-SH and DBT5-H had maximum hole mobility (μh) values of 6.031 × 10–2 and 1.140 × 10–2 which were greater than those measured for the reference DBT5 molecule (μh = 3.984 × 10–4 cm2/V/s) and about 10 and 100 times superior to the calculated and experimental μh values for well-known Spiro-OMeTAD. The DBT5-COOH illustrated the biggest open circuit voltage (VOC), fill factor (FF) and power conversion efficiency (PCE) values of 1.166 eV, 0.896 and 23.707%, respectively, establishing it could be as the best HTM candidate for high performance PSCs.

Recent studies on small molecular and polymeric hole‐transporting materials for high‐performance perovskite solar cells

“…They reported that difunctionalized BTZI‐TPA exhibited a high efficiency of 24.06% due to the better‐aligned energy levels, stronger interaction with uncoordinated Pb 2+ on the perovskite surface, and suppressing charge carrier nonradiative recombination (NRR) and carrier accumulation at the interface of the perovskite/spiro‐OMeTAD [58]. Various butterfly‐shaped materials composed of dibenzodithiophene (DBT5) units were developed by Sarmalek et al, and their properties were studied by density functional theory (DFT) computations for usage as HTMs in mesoscopic n‐i‐p PSCs, achieving the highest PCE of 23.70% for the DBT5‐COOH molecule [59]. Through molecular engineering, new acridine‐based HTMs have been synthesized by replacing the PTZ core and analyzing the effects of peripheral groups on the acridine core.…”

Graphene quantum dots (GQD) and edge-functionalized GQDs as hole transport materials in perovskite solar cells for producing renewable energy: a DFT and TD-DFT study

“…Eqn (1) and ( 2) were used to calculate the light harvesting efficiency (LHE) and exciton binding energy (E b ) of molecules considered GQDs. [45][46][47]…”

“…Eqn (1) and (2) were used to calculate the light harvesting efficiency (LHE) and exciton binding energy ( E b ) of molecules considered GQDs. 45–47 E b = E g − E opt where, f abs max is the oscillator strengths for the maximum absorption peak. E g is defined as the gap energy between the HOMO and LUMO whereas E opt is optical bandgap which is the gap energy between electronic ground state and first excited state.…”

Theoretical investigations of the substituent effect on the opto‐electronic properties of the linearly fused napthadithiophene‐based molecules

“…Among them, thiophene‐based materials have gained considerable attention due to their ability to tune the physical properties of OSC, such as electronic structure, frontier molecular orbital energy levels, optical properties, and charge carrier mobility 12,13 . In particular, benzodithiophene (BDT) and anthradithiophene (ADT) materials were identified as solution‐processable p‐type and n‐type materials in OFETs and OPVs in recent years 14–18 . Masashi Mamada et al synthesized syn and anti‐configurations of ADT and found differences in the physical properties between them 19 .…”

“…and anthradithiophene (ADT) materials were identified as solutionprocessable p-type and n-type materials in OFETs and OPVs in recent years. [14][15][16][17][18] Masashi Mamada et al synthesized syn and anticonfigurations of ADT and found differences in the physical properties between them. 19 In particular, the p-channel FET mobility of the anti-ADT derivative (0.42 cm 2 V À1 s À1 ) was higher than that of the syn-ADT (0.12 cm 2 V À1 s À1 ) derivative.…”