Critical binding energy for exciton dissociation and its implications for the thermodynamic limit of organic photovoltaics

M. Khan, M. Alam
{"title":"Critical binding energy for exciton dissociation and its implications for the thermodynamic limit of organic photovoltaics","authors":"M. Khan, M. Alam","doi":"10.1109/DRC.2014.6872406","DOIUrl":null,"url":null,"abstract":"Spectroscopic signatures of strongly bound excitons (binding energy, E<sub>B</sub>) in various low dielectric constant materials and reduced dimensional systems, such as CNT transistors, Quantum well lasers, etc. are often erased during room temperature, high-field, high-power-density operation of these devices. Similarly, while pump-probe experiments have been used extensively to explore exciton dynamics in organic photovoltaics (OPVs), one wonders if the exciton bottlenecks would persist under continuous broadband illumination of OPV. In this paper, we use a self-consistent thermodynamic model (involving detailed-balance and energy-conservation) to explicitly model the kinetics of exciton dissociation and corresponding energy balance considerations [1,2]. We find that exciton bottleneck may arise under normal PV operation if and only if the exciton binding energy, E<sub>B</sub> > <sub>B(critical)</sub> ≡ (p<sub>therm</sub> + ΔE)× J<sub>sc</sub>/J<sub>opt</sub>, where J<sub>sc</sub> and J<sub>opt</sub> are the short-circuit and maximum power point currents, with the ratio~1; the thermalization per carrier is given by p<sub>therm</sub> ≈ P<sub>therm</sub>/(J<sub>SC</sub>) ≈ ((4+ξ+6/ξ)/(2+ξ)) kT<sub>s</sub> (for an ideal blackbody source), with ξ = E<sub>G</sub>/kT<sub>s</sub>. And, ΔE is the type-II band-discontinuity of a bulk-heterojunction (BHJ) cell. We predict that all signatures of exciton-limited performance of OPV would be eased if E<sub>B</sub> <; E<sub>B(critical)</sub>, and the operation of an OPV would be indistinguishable from their classical counterparts.","PeriodicalId":293780,"journal":{"name":"72nd Device Research Conference","volume":"13 1 1","pages":"0"},"PeriodicalIF":0.0000,"publicationDate":"2014-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"72nd Device Research Conference","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1109/DRC.2014.6872406","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 1

Abstract

Spectroscopic signatures of strongly bound excitons (binding energy, EB) in various low dielectric constant materials and reduced dimensional systems, such as CNT transistors, Quantum well lasers, etc. are often erased during room temperature, high-field, high-power-density operation of these devices. Similarly, while pump-probe experiments have been used extensively to explore exciton dynamics in organic photovoltaics (OPVs), one wonders if the exciton bottlenecks would persist under continuous broadband illumination of OPV. In this paper, we use a self-consistent thermodynamic model (involving detailed-balance and energy-conservation) to explicitly model the kinetics of exciton dissociation and corresponding energy balance considerations [1,2]. We find that exciton bottleneck may arise under normal PV operation if and only if the exciton binding energy, EB > B(critical) ≡ (ptherm + ΔE)× Jsc/Jopt, where Jsc and Jopt are the short-circuit and maximum power point currents, with the ratio~1; the thermalization per carrier is given by ptherm ≈ Ptherm/(JSC) ≈ ((4+ξ+6/ξ)/(2+ξ)) kTs (for an ideal blackbody source), with ξ = EG/kTs. And, ΔE is the type-II band-discontinuity of a bulk-heterojunction (BHJ) cell. We predict that all signatures of exciton-limited performance of OPV would be eased if EB <; EB(critical), and the operation of an OPV would be indistinguishable from their classical counterparts.
激子解离的临界结合能及其对有机光伏电池热力学极限的影响
在各种低介电常数材料和降维系统(如碳纳米管晶体管、量子阱激光器等)中,强束缚激子(结合能,EB)的光谱特征在这些器件的室温、高场、高功率密度操作过程中经常被擦除。同样,虽然泵浦探针实验已被广泛用于探索有机光伏(OPV)中的激子动力学,但人们想知道在OPV的连续宽带照明下,激子瓶颈是否会持续存在。在本文中,我们使用一个自洽热力学模型(包括详细平衡和能量守恒)来明确地模拟激子解离动力学和相应的能量平衡考虑[1,2]。我们发现,当且仅当激子结合能EB b> B(临界)≡(ptherm + ΔE)× Jsc/Jopt,其中Jsc和Jopt分别为短路点电流和最大功率点电流,比值为~1时,PV正常工作时激子瓶颈可能出现;每个载流子的热化率为:ptherm≈ptherm /(JSC)≈(4+ξ+6/ξ)/(2+ξ)) kTs(对于理想黑体源),ξ = EG/kTs。其中ΔE为块体异质结(BHJ)电池的ii型带不连续。我们预测,当ebb达到临界时,OPV的激子限制性能的所有特征都将得到缓解,并且OPV的操作将与经典的OPV无法区分。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
自引率
0.00%
发文量
0
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信