Application Of Fullerene And Its Derivatives In Polymer/Perovskite Solar Cells

Recently,Polymer solar cells(PSCs)and Perovskite solar cells(Pero-SCs)have become a research focus,due to their light weight,low-cost processing and the possibility of fabricating into flexible devices.Great efforts have been devoted to further improving the power conversion efficiencies(PCEs)of PSCs and Pero-SCs.Among them,the application of fullerene and fullerene derivatives as acceptors and electron transport materials in PSCs and Pero-SCs has attracted extensive attention.This thesis focused on the application of fullerene derivatives in PSCs and Pero-SCs.This research includes a full investigation of the regioisomers effect of fullerene bisadduct IC60BA as acceptors on the performance of PSCs,as well as the effects of a series of novel fullerene derivatives as cathode interface modification layer on the performance of Pero-SCs were also thoroughly discussed.The details are as follows:(1)Towards a full understanding of regioisomer effects of indene-C60 bisadduct acceptors on the photovoltaic performance of PSCs:Major regioisomers of IC60BA were isolated,and a full investigation of their structure,abundance,solubility and the effect of these regioisomers on the device performance of the PSCs with P3HT as donor were carried out for the first time.It was found that the commonly used IC60A acceptor of PSCs had 12 major isomers and the corresponding devices based on these 12 regioisomers presented very diverse PCEs(from 0.03%to 6.06%,measured by a Keithley 2400 source meter).In particular,PSCs based on trans-3(a)and e-2 regioisomers demonstrated high PCE of 6.06%and 5.38%,respectively,which was superior to the PSC with IC60BA mixture(5.19%).This study revealed that,the energetic disorder inside the regioisomers did not have major effect on the PCE of PSCs.However,when these isomers applied as acceptors in PSCs,the relative indene positions,the steric orientation of indene groups and the solubility of these regioisomers could dramatically affect the morphology of active layer,which led to a very different PCE of PSCs based on IC60BA regioisomers as acceptor.(2)Facilitating electron transportation in perovskite solar cells via water-soluble fullerenol interlayers:An easy-accessible hydroxylated fullerene derivative,fullerenol(C60(OH)24-26),was applied to modify TiO2 electron transport layer(ETL)of Pero-SCs for the first time.And a full investigation for the effect of fullerenol on device performance was carried out.It was found that,after the introduction of fullerenol interlayer,the energy level band gap between CH3NH3PbI3-xClx perovskite and ETL was decreased,which was beneficial for the improvement of Voc in Pero-SCs.Moreover,the device with fullerenol modification layer showed improved charge transportation,high crystallinity of perovskite film and decreased interfacial resistance.As a result,the device based on TiO2/fullerenol ETL obtained an enhanced power conversion efficiency(PCE)of 14.69%,which was a～17.5%improvement compared to the control device(12.50%)with pristine TiO2 ETL.(3)Interfacial engineering via inserting functionalized water-soluble fullerene derivative interlayers for enhancing the performance of perovskite solar cells:Two novel functionalized water-soluble fullerene derivative C60O～18(OH)-10(NH2)～8(f-C60)and C70O～18(OH)～10(NH2)～10(f-C70)were synthesized and applied as modification layer in Pero-SCs.And the devices based on ITO/f-C60 or f-C70/C60/CH3NH3PbI3-xClx perovskite/P3HT/MoO3/Ag were fabricated to evaluate the effect of f-C60 and f-C70 on device performance.The results showed the pristine C60 ETL based Pero-SCs obtained a PCE of 13.71%,and the devices based on f-C60/C60 and f-C70/C60 ETL showed significantly enhanced PCE of 16.97%and 15.94%,respectively.Furthermore,the systematic studies and characterizations exhibited that,the introduction of f-C60 and f-C70 interlayer could simultaneously facilitate the electron transport and reduce the charge recombination.This work suggested that f-C60 and f-C70 as an interlayer have great potential on the application in Pero-SCs.(4)Fullerene derivative-modified SnO2 electron transport layer for highly efficient perovskite solar cells:A C60 substituted phenol pyrrolidinofullerene derivative(NPC60-OH)was employed to modify SnO2 ETL in Pero-SCs.The NPC60-OH fullerene derivative was synthesized via a facile one-step method under a low temperature of 125℃.Furthermore,after the modification of NPC60-OH layer,the electrons were transported more efficiently from perovskite active layer to ETL and the charge recombination was decreased.Besides,the perovskite film deposited on SnO2/NPC60-OH ETL showed an enlarged average grain size of 360 nm,while the perovskite film based on pristine SnO2 only obtained the grain size of 310 nm.As a consequence of the abovementioned factors,the Pero-SCs with SnO2/NPC60-OH ETL achieved a champion PCE of 21.39%with improved stability,which was superior to the control device(19.04%).(5)Pyridine based pyrrolidinofullerene derivatives as interface modification layer for enhancing performance of perovskite solar cells:Three pyridine based pyrrolidinofullerene derivatives with different nitrogen sites(Ortho-C60,Meta-C60 and Para-C60)were synthesized and applied as modification layer in Pero-SCs.The effect of heteroatom site of fullerene derivatives on the device performance has been investigated.It was found that Ortho-C60,Meta-C60 and Para-C60 fullerene derivatives demonstrated negligible difference in optical absorption and energy levels.However,the Pero-SCs with these fullerene derivatives exhibited different PCE.The device based on Meta-C60 modified SnO2 presented the highest PCE of 19.31%,which was 11.6%improvement compared with the control device(17.30%).The DFT calculation results suggested that Meta-C60 showed stronger coordination interaction with Pb2+of MAPbI3 perovskite layer than the Ortho-C60 and Para-C60 fullerene derivative,which give rise to the enhanced PCE of Meta-C60 based devices.