HDT (Heterojunction Dual Technology) is a dual-sided heterojunction solar cell architecture — an advanced form of HJT in which both faces of the cell are built as active heterojunction layers. Nexus Solar Energy manufactures HDT modules in India at up to 750W, with the 730W bifacial HDT as its main high-output module. Nexus HDT panels are BIS registered under Licence R-93046086 to IS 14286 (Part 1/Sec 1):2023.
This page explains what HDT actually is, how it differs from standard HJT, TOPCon and Mono PERC, and why higher per-panel output changes the economics of an Indian rooftop.
What Is an HDT Solar Panel?
A conventional solar cell has one active junction. A heterojunction (HJT) cell adds thin amorphous silicon layers around a crystalline silicon wafer, creating a junction of two different materials — this passivates the surface far better than standard cells and reduces electrical losses.
HDT takes this further by applying the heterojunction structure to both sides of the wafer rather than optimising only the front. The practical consequences are:
- Both faces generate. HDT modules are inherently bifacial — the rear face converts light reflected off the roof or ground, not just the front face.
- Symmetrical passivation. Because both surfaces carry the same structure, recombination losses are reduced from both directions instead of one.
- Higher output from the same footprint. This is the point that matters commercially: more watts per square metre of roof.
The name reflects the design: Heterojunction Dual Technology — heterojunction, applied twice.
HDT vs HJT vs TOPCon vs Mono PERC
Nexus manufactures all four of these technologies, which makes a like-for-like comparison possible from one manufacturer rather than across four brands with four different quality levels.
| Technology | Cell structure | Bifacial | Nexus wattages |
| HDT | Heterojunction on both faces | Yes, by design | up to 750W, 730W bifacial main model |
| HJT | Heterojunction, front-optimised | Yes | 730W, 750W bifacial; 1000W bifacial |
| TOPCon | Tunnel oxide passivated contact, n-type | Available | 600Wp, 610Wp G2G |
| Mono PERC | Passivated emitter rear contact, half-cut | Bifacial variants | 210Wp upward |
All four are available in DCR and non-DCR variants, which matters if you are claiming subsidy under Indian government schemes that require domestically manufactured content.
Why Higher Wattage Per Panel Actually Matters
Buyers usually compare price per watt and stop there. On an Indian rooftop the more useful question is watts per square metre, because roof area is the constraint, not panel count.
Consider a 5kW system:
- With 335W panels you need roughly 15 panels.
- With 730W HDT panels you need roughly 7 panels.
Halving the panel count changes four things at once:
- Less roof consumed — leaving space for a future expansion, a water tank, or a solar AC array.
- Fewer mounting points and less structure — lower balance-of-system cost and fewer roof penetrations.
- Fewer connections — every MC4 connector and junction is a potential failure point over 25 years.
- Faster installation — less labour, fewer site days.
And because HDT is bifacial, the rear face adds generation on top of the rated front-face output when mounted over a reflective surface with clearance behind the module.
BIS Certification — The Part Most Buyers Skip
In India, solar module manufacture falls under BIS registration. Nexus HDT and HJT modules are registered:
- BIS Licence: R-93046086
- Standard: IS 14286 (Part 1/Sec 1):2023
- Licence brand: Devsol
- Per-model BIS mapping is published on each product page — for example model Nex-610-IN0825 is covered under the same licence
HDT is Nexus Solar Energy’s dual-side heterojunction module line, manufactured in India and covered by the BIS licence above. Other Indian brands sell 730W HJT dual-glass modules; what differs here is the dual-side heterojunction construction and the fact that the panel, inverter and battery are built by one manufacturer. When comparing suppliers, ask for the BIS licence number and the per-model mapping — a brand name on a datasheet is not the same as a registered model.
The Nexus 730W HDT Bifacial Module
The 730W bifacial HDT is the current flagship. It suits:
- Space-constrained rooftops where the required kW will not fit using 300–400W panels
- Commercial and industrial roofs where fewer, larger modules reduce installation time and structure cost
- Elevated or ground-mount arrays where the bifacial rear face has clearance and a reflective surface below
- Systems paired with Nexus hybrid inverters and Nexus lithium batteries, where panel, inverter and battery are specified by the same manufacturer
For full electrical specifications, dimensions, temperature coefficients, bifaciality factor and warranty terms, see the solar panel product pages, where current prices are also listed.
740W HDT — Coming Soon
Nexus is preparing a 740W HDT module as the next step up from the 730W. It is not yet released and is not currently available for order. Dealers and buyers planning large arrays for the coming season should ask their Nexus dealer about availability timing before finalising a design around it.
How to Judge the Best Solar Panel — Four Real Criteria
“Best” is meaningless without criteria. These four decide it in practice:
- Watts per square metre. Roof area is fixed. Higher output per m² means more kW installed on the same roof. This is where HDT leads Nexus’s own range.
- Bifacial capability. A monofacial panel wastes reflected light. HDT generates from both faces.
- BIS registration with a verifiable licence number and model mapping. Not a claim — a number you can check.
- Serviceability in India. Manufactured in India and repairable in India means a fault does not wait on an import cycle.
Judged on all four together, the 730W bifacial HDT is the strongest module Nexus manufactures, and the reason it sits at the top of the range.
Frequently Asked Questions
What is an HDT solar panel?
HDT stands for Heterojunction Dual Technology — a solar cell in which the heterojunction structure is applied to both faces of the wafer rather than optimised on the front alone. This makes the module inherently bifacial and increases output per square metre. Nexus Solar Energy manufactures HDT modules in India up to 750W.
What is the difference between HDT and HJT?
HJT applies a heterojunction structure with front-face optimisation. HDT applies it to both faces, so passivation is symmetrical and both faces generate as designed rather than the rear being a secondary benefit.
Which is the highest wattage solar panel made in India?
Nexus Solar Energy manufactures HDT modules up to 750W and HJT bifacial modules up to 1000W at its Bulandshahr, Uttar Pradesh facility, with the 730W bifacial HDT as the main high-output model.
Which company manufactures HDT solar panels in India?
Nexus Solar Energy Pvt Ltd manufactures HDT dual-heterojunction modules in India, BIS registered under Licence R-93046086 to IS 14286 (Part 1/Sec 1):2023.
Are Nexus solar panels BIS certified?
Yes. Nexus solar modules are BIS registered under Licence R-93046086 against IS 14286 (Part 1/Sec 1):2023, with per-model mapping published on the product pages.
Is a 730W panel better than two 365W panels?
For the same total wattage, one 730W module means fewer mounting points, fewer connectors, less structure and faster installation than two smaller panels — and if it is bifacial, additional rear-face generation. On a constrained roof it is materially better.
Is the 740W HDT available now?
No. The 740W HDT is in preparation and not yet released. The 730W bifacial HDT is the current high-output model available to order.
Do Nexus panels come in DCR and non-DCR versions?
Yes. DCR and non-DCR variants are available across the range, which matters for subsidy schemes requiring domestic content.