Modulation of metal free organic (MFO) molecules become imperative to researchers to obtain low-cost sensitizer for dye sensitized solar cells (DSSCs) purposes. A series of metal free phenothiazine-based (PTZ) organic dyes are designed and optimized as sensitizers for DSSCs application. Their electronic and optical properties were probed using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) approaches. Effects of additional donor unit, π-conjugation bridges, and benzothiadiazole (BTDA) were investigated. Introducing BTDA in the acceptor unit leads to the tailoring of the energy band gap and promotion of charge transfer within donor and anchor groups with increased effective parameters in DSSC efficiency. The addition of diphenylamine, triphenylamine, or hexyloxyphenyl to the PTZ unit increased electron delocalization and enhanced intramolecular charge transfer. Changing π-spacer from phenyl to thiophene has a great effect on the electronic properties and absorption spectra of the dyes. The relationship between light harvesting efficiency (LHE) and chemical hardness (ƞ) shows that structural design that consists of BTDA and thiophene as π-spacer tends most towards excellent performance as dye sensitizers in DSSCs.

中文翻译：

---

吩噻嗪基低带隙染料衍生物作为分子光伏敏化剂的设计与理论研究

无金属有机 (MFO) 分子的调制对于研究人员获得用于染料敏化太阳能电池 (DSSC) 目的的低成本敏化剂来说变得必不可少。一系列无金属吩噻嗪 (PTZ) 有机染料被设计和优化为 DSSC 应用的敏化剂。使用密度泛函理论 (DFT) 和瞬态密度泛函理论 (TD-DFT) 方法探测了它们的电子和光学特性。研究了额外的供体单元、π-共轭桥和苯并噻二唑 (BTDA) 的影响。在受体单元中引入 BTDA 可调整能带隙并促进供体和锚定基团内的电荷转移，并增加 DSSC 效率的有效参数。加入二苯胺、三苯胺、或己氧基苯基到 PTZ 单元增加了电子离域并增强了分子内电荷转移。将π-间隔基从苯基变为噻吩对染料的电子性质和吸收光谱有很大影响。光收集效率 (LHE) 和化学硬度 (ƞ) 之间的关系表明，由 BTDA 和噻吩作为 π 间隔物组成的结构设计最倾向于作为 DSSC 中染料敏化剂的优异性能。