The low-lying excited states of zethrene, its homologs, and conjugated molecules like bis-phenaleno-indenofluorene, diaryl pentaleno diacenaphthylene and pentalenodiphenalene have been calculated using the Density Matrix Renormalization Group (DMRG) method within model Pariser-Parr-Pople(PPP) Hamiltonian. DMRG calculation shows that the energy ordering of low-lying singlet and triplet excited states of most of these molecules with 4$n\pi$ electrons satisfy two essential energetic conditions related to singlet fission (SF), a multiexcitonic process where one singlet exciton converts into two triplet excitons generating more number of charge carriers with longer lifetime enhancing the photoelectric conversion efficiency(PCE) in solar cell applications. The lowest singlet and triplet excited states calculated in DMRG are in very good agreement with experimental results in the literature. Such low-lying excitations and intermediate diradical characters of these molecules calculated through projected spin unrestricted Hartree-Fock (PUHF) method establish the fact that these molecules are potential candidates for designing SF materials.

在模型Pariser-Parr-Pople（PPP）模型中，使用密度矩阵重整化组（DMRG）方法计算出了蒽的低激发态，其同系物以及共轭分子，例如双-苯并-茚并芴，二芳基戊二烯二ac和戊烯二苯哈密​​尔顿 DMRG计算表明，大多数这些分子的低态单重态和三重态激发态的能级为4$ñ\pi$电子满足与单线态裂变（SF）有关的两个基本能量条件，这是一种多激子过程，其中一个单线态激子转换为两个三线态激子，从而产生更多数量的电荷载流子，具有更长的寿命，从而提高了太阳能电池应用中的光电转换效率（PCE）。用DMRG计算的最低单重态和三重态激发态与文献中的实验结果非常吻合。通过投影自旋无限制Hartree-Fock（PUHF）方法计算得出的这些分子的低激发和中间双自由基特性证明了这些分子是设计SF材料的潜在候选者。