Several universal issues such as environmental concerns, limited supply of fossil fuels, and rising energy demand have led to research on renewable energies. In this regard, one of the most promising ways to meet future demand without negatively affecting the global climate is the conversion of solar energy into electricity as a clean energy source [1]. However, in the solar cell industry, energy consumption and the cost of large-scale manufacturing processes are key challenges. So low manufacturing cost and high-power conversion efficiency can be achieved through materials and devices selection. Emerging Perovskite solar cells (PSCs) are characterized by their ease of processing and low cost, they have attracted a lot of attention due to their many advantages like the ambipolar nature of perovskites, and the wide light absorption [2]. Regardless of the PSC device architecture, the most effective way to improve the stability of PSCs and the photoelectric conversion is using a high-performance hole-transporting material (HTM). HTM reacts as an essential layer to ensure transport processes and efficient charge separation at material interfaces [3]. To enhance the efficiency of PSCs, different types of HTMs have been developed and fabricated [[4], [5], [6]]. P-type organic small molecule, polymer hole conductors are in most cases used as HTMs for PSCs, mainly due to their low visible light absorption, simplicity, ease of purification, and good solid-state morphology [[7], [8], [9]]. These materials have several disadvantages in commercialization due to their multistep synthesis which leads to high cost and the need for hygroscopic dopants that induce perovskite layer degradation in their deposition processes. Different organic HTMs such as poly(triarylamine) (TPAA) [[10], [11], [12]] 2,2ʹ,7,7ʹ-tetrakis (N,N-di-p-methoxyphenylamine)-9,9ʹ-spirobifluorene (spiro-OMeTAD) [7,13,14], and poly(3-hexylthiophene) (P3HT) [15,16] have been fabricated but they still suffering from device degradation and reduced stability of PSC associated to dopants, and additives in HTM. Therefore, addressing stability issues by developing dopant-free HTMs remains a challenging and convincing study. Carbazoles have good optical properties, low redox potential, and high chemical stability, which is why oligo/polycarbazoles have been the representative reference materials in OFETs, OLEDs, and OSCs [[17], [18], [19], [20], [21]]. Poly(3,6-carbazole) and 3,6-functionalization Carbazoles have been extensively explored in the past few decades because carbazoles can be easily functionalized with high electron density through electrophilic substitution at their 3,6 positions (para position to nitrogen atom). Recent developments in carbazole chemistry have also established efficient routes for the synthesis of 1,8- and 2,7-functionalized carbazoles and revealed their special properties that are distinctly different from 3,6-carbazole derivatives [[22], [23], [24]]. In this case, carbazole can be considered as an important scaffold for building π-functional materials because of its abundant structural modifications. Mixed π-conjugated carbazole and thiophene units have attracted significant attention for various material applications, building on the well-established research on oligothiophenes, particularly α-oligothiophenes [25]. Oligomers have recently gained considerable popularity because of their potential as active ingredients for organic electronics and their synthetic accessibility. Due to their fluorescent and donor properties, various carbazole-thiophene hybrid oligomers have been reported as functional materials [26]. Since the pioneering work of Koumura, Hara and colleagues [27,28], many derivatives containing anchoring and acceptor groups for OSCs have been synthesized. Less attention has been paid to elucidating the structure-property relationships in carbazole-thiophene-based π-systems, which are essential for material design. In 2022, Hu et al. [29] have used two monomers M1 and M2 based on 9-(4-(thiophen-2-yl)phenyl)-9H-carbazole thiophene-phenyle (head) and carbazole (core), substituted by thiophene in 3,6 and 2,7 of carbazole positions, in synthesizing of polymers for electrochromic application. In this study, we build on the structures of these two molecules (M1 and M2) to suggest group modifications for the design of four new molecules (P1, P2, E1, E2) by conserving the M1,2 (head, core) and changing the extremities with anisole and diphenyl amine (DMPA). The 4,4′-dimethoxydiphenylamine (DMPA) units, which include nitrogen, are incorporated in the majority of small molecule HTMs. To increase hole mobility, nitrogen atoms are added since they are hole-acceptors. The passivation of defect sites on the perovskite crystal surface, which enhances charge extraction at the perovskite/HTM interface and device stability [30,31] was used to demonstrate that the electron-rich methoxy units are involved in this process. Herein we will study the availability of the six molecules for HTMs application based on various theoretical parameters.