%0 Journal Article %1 doi:10.1021/acsenergylett.6b00727 %A Sutter-Fella, Carolin M. %A Miller, D. Westley %A Ngo, Quynh P. %A Roe, Ellis T %A Toma, Francesca M. %A Sharp, Ian D. %A Lonergan, Mark C %A Javey, Ali %D 0 %J ACS Energy Letters %K defects perovskite tailstates %N ja %P null %R 10.1021/acsenergylett.6b00727 %T Band Tailing and Deep Defect States in CH3NH3Pb(I1-xBrx)3 Perovskites as Revealed by Sub-Bandgap Photocurrent %U http://dx.doi.org/10.1021/acsenergylett.6b00727 %V 0 %X Organometal halide perovskite semiconductors have emerged as promising candidates for optoelectronic applications because of the outstanding charge carrier transport properties, achieved with low temperature synthesis. Here, we present highly sensitive sub-bandgap external quantum efficiency (EQE) measurements of Au/spiro-OMeTAD/CH3NH3Pb(I1-xBrx)3/TiO2/FTO/glass photovoltaic devices. The room temperature spectra show exponential band tails with sharp onset characterized by low Urbach energies (Eu) over the full halide composition space. The Urbach energies are 15 - 23 meV, lower than for most semiconductors with similar bandgaps (especially with Eg > 1.9 eV). Intentional aging of CH3NH3Pb(I1-xBrx)3 for up to 2300 hours, reveals no change in Eu, despite the appearance of PbI2 phase due to decomposition, and confirms a high degree of crystal ordering. Moreover, sub-bandgap EQE measurements reveal an extended band of sub-gap electronic states that can be fit with one or two point defects for pure CH3NH3PbI3 or mixed CH3NH3Pb(I1-xBrx)3 compositions, respectively. The study provides experimental evidence of defect states close to midgap that could impact photocarrier recombination and energy conversion efficiency in higher bandgap CH3NH3Pb(I1-xBrx)3 alloys.

@article{doi:10.1021/acsenergylett.6b00727, abstract = { Organometal halide perovskite semiconductors have emerged as promising candidates for optoelectronic applications because of the outstanding charge carrier transport properties, achieved with low temperature synthesis. Here, we present highly sensitive sub-bandgap external quantum efficiency (EQE) measurements of Au/spiro-OMeTAD/CH3NH3Pb(I1-xBrx)3/TiO2/FTO/glass photovoltaic devices. The room temperature spectra show exponential band tails with sharp onset characterized by low Urbach energies (Eu) over the full halide composition space. The Urbach energies are 15 - 23 meV, lower than for most semiconductors with similar bandgaps (especially with Eg > 1.9 eV). Intentional aging of CH3NH3Pb(I1-xBrx)3 for up to 2300 hours, reveals no change in Eu, despite the appearance of PbI2 phase due to decomposition, and confirms a high degree of crystal ordering. Moreover, sub-bandgap EQE measurements reveal an extended band of sub-gap electronic states that can be fit with one or two point defects for pure CH3NH3PbI3 or mixed CH3NH3Pb(I1-xBrx)3 compositions, respectively. The study provides experimental evidence of defect states close to midgap that could impact photocarrier recombination and energy conversion efficiency in higher bandgap CH3NH3Pb(I1-xBrx)3 alloys. }, added-at = {2017-02-20T09:46:38.000+0100}, author = {Sutter-Fella, Carolin M. and Miller, D. Westley and Ngo, Quynh P. and Roe, Ellis T and Toma, Francesca M. and Sharp, Ian D. and Lonergan, Mark C and Javey, Ali}, biburl = {https://www.bibsonomy.org/bibtex/2206d5220b161859343ca99f1ac1ac009/fabianopkm}, doi = {10.1021/acsenergylett.6b00727}, eprint = {http://dx.doi.org/10.1021/acsenergylett.6b00727}, interhash = {7f1e667655c8c63217dd95cbc03b81a2}, intrahash = {206d5220b161859343ca99f1ac1ac009}, journal = {ACS Energy Letters}, keywords = {defects perovskite tailstates}, number = {ja}, pages = {null}, timestamp = {2017-02-20T09:46:38.000+0100}, title = {Band Tailing and Deep Defect States in CH3NH3Pb(I1-xBrx)3 Perovskites as Revealed by Sub-Bandgap Photocurrent}, url = {http://dx.doi.org/10.1021/acsenergylett.6b00727}, volume = 0, year = 0 }